During Phase II developmental work on a continuous flow ultrasonic plasma/blood cell separator TRA found that it was able to band and move blood cells (thus separating them from plasma) in micro-hematocrit tubes. This new ultrasonic process produces forces up to 5000 times that of gravity on particles, thus is comparable to centrifuge techniques. Cavitation of the medium does not occur and is not required for the device to operate. This capability allows the development of a device which will rapidly, in a matter of seconds, determine hematocrit from blood contained in an hematocrit tube as well as allow the collection of cell free plasma to be subsequently used for analysis of various plasma parameters. This capability will greatly assist medical personnel in the delivery of emergency medical care by providing cardiovascular system information. Because very small quantities of blood will be required, extensive use of this device in neonatal care is expected. Phase I will demonstrate the feasibility of the device and provide the framework and data necessary for Phase II development. The end product will be a totally portable hematocrit measuring apparatus about the size of a hand-held digital multimeter. This small device will have low power consumption (1-2 watts) and since it has no moving parts, will be inherently reliable. An alternate version of the device will provide, in addition, cell free plasma.